Time-delay relay testing device



Oct. 28, 1952 c. B. GOULD TIME-DELAY RELAY TESTING DEVICE Filed May 26, 1947 INVENTOR. Char/e6 .3 60a la Patented Oct. 28, 1952 TI -DELAY RELAY TESTING VIC Charles B. Gould, Cleveland, Ohio assignor to the United States of America as represented by the United States Atomic Energy Commission Application May '26, 1947, Serial No; 759,466

3 laims. 1

This invention pertains to a novel electrical circuit for measuring the time-delay of a time delay relay,

As is well known in the art, a time-delay relay commonly has controlling terminals and controlled contacts. The essence of the operation of the time-delay relay is the time lag which exists between the instant of changing the status of the potential applied to-the controlling terminals and the subsequent actuation of the controlled contacts. The change of status of the potential applied to the controlling terminals may be either the application or removal of a voltage, and the actuation of the controlled contacts may be such as either to open or to close an electrical circuit which is controlled by the relay. Various types of time-delay relays are in use, the most common types bein the thermal type and the clock-work type.

It is the principal object of this invention to provide a novel electrical circuit for measuring the time-delay of a time-delay relay. Other aims and objects will appear'from the description below and from the drawing, in which is depicted a schematic electrical diagram of a circuit for measuring the time-delay of a time-delay relay incorporating the teachings of the invention.

Referring to the drawing, a source of direct voltage is connected across a series combination of a potentiometer l2 and two voltageregulator tubes l4 and It, the positive terminal of the voltage source IIJ being connected to the potentiometer l2. The potential appearing across the tapped portion of thepotentiometer I2 is connected to the windings l8 of a conventional solenoid relay through the normally open controlled contacts 22 of a time-delay relay 24, whose time-delay is under measurement.

As illustrated in the drawing, the timerdelay relay is of the thermal type wherein a potential applied ,to the controlling terminals heats ,a resistance element which causes the bending of a bi-metallic member, thus closing thecontrolled contacts 22. However, it will be understood that the circuit of the drawin may be used with any type of time-delay relay.

The voltage across the potentiometer l2 and the voltage-regulator tube l4 acts as a voltage supply for the controlling terminals 25 of the time-delay relay 24. The controlling terminals 26 are in the plate circuit of avacuum tube 28, the plate current of which is controllable by a variable resistance 30 in the cathode circuit. The plate current of the tube 28, and thus the current flowin through the controlling terminals 26 of the time-delay relay 2d, may be read from the milliammeter 32 which is connected in series therewith.

The potential across the voltage-regulator tube I4 constitutes the voltage supply for a vacuum tube 35 which has a condenser 38 connected beween t e gri an cath de ,there f- Thea i f the vacuum tub .36 i eenneet d hr egliree an es 4B a 42 and t e norma l closed ont ct 44 eithe re ay 2.0 to the tense tr -e e r 6, whi h is enneeted n se i s w afi e re tan e 48 ac s th ,veltase e ulate? tu The ta on the po e t m er .45 is n t in e t withre p e t the e thege o the acuu t b 6- The n io b e t e gri r tube .ee and the tap on the potentiometerfifi is land? through a terminal of a tw0-position select or switch 59 which is ganged with a similar twoposition selector switch 52 which is inthecat'hode circuit of the vacuumtube 28. The selector switches 50 and 52 each have two positions designated inthe drawin as and Y. Whenthe switchestfl and 52 are in the position Y, the connections are as described above. When the switches 50 an d 52 are, however, in the position X, the cathode circuit of'the vacuum 'tube'28 is open, thus allowing no current toflow through the controlling'terminals 26 of the time-delay relay 24. Also, when the switches are in the position X, the grid of the vacuum tube 3-6 is connected to the junction between the fixed resistance '48 and the potentiometer 46, which point is less negative with-'repect to the cathode of the vacuum tube 36 than'is the tap on the potentiometer "46.

Persons skilled in-the art will readily see that when the switch 50 is in the position 5;, the condenser 38 will charge up to the potential appearing across-the resistance 48. ;Such charge on the condenser 38 will then constitute a negative bias on the grid'of the vacuum tube 36. "The corresponding plate currentof the vacuumtube 36 may be read from-a milliammeter 54, shunted by a variable resistance 56, inthe plate circuit of the vacuum tube 36. When the switch :50 is switched to position Y, the condenser -38 will commence to charge to a potentialsuchthat the grid of the vacuum-tube 36 isturther negative with respect to the cathode. As the grid becomes more negative with respect to the cathode, the plate current in the tube -3-6-wi-ll decrease correspondingly. The rate of charging of the condenser 38 is determined by the capacitance of the condenser 38 and the resistance of the resistors 40 and 42. As is well known in the art,-for times whichare short compared to the time constant of the resistance and capacitance, -;the charging of the condenserwill be linearp-that is to say, the negative voltage of the grid of :the tube 36 with respect to the cathode will increase -linear 1y with elapsed time. The vacuum tube 3 6is operated at a linear portion of its characteristic, i. e., in a region Where the decrease in plate current varies linearly with the increase in negative r voltage hi s eeeemplie e rb the bia provided in the manner above stated before the switch 50 is thrown to position Y. Thus, the current indicated on the milliammeter 54 decreases linearly with time when the switch 50 is thrown to position Y.

The operation of the circuit illustrated in the drawing in measuring the time-delay of the timedelay relay 24 may now easily be understood. Preparatory to making the measurement, the switches 50 and 52 are maintained in the X position. In this position, the current through the milliammeter 54 preferably deflects the indicator thereon to full-scale. No current flows to the controlling terminals 26 of the time-delay relay 24 because the cathode circuit of the tube 28 is open. The contacts 44 of the relay 20 are closed since the controlled contacts 22 of the time-delay 24 are open, and thus allow no current iiow through the windings 18 of the relay 20.

When the measurement is to be made, switches 50 and 52 are thrown to the Y position. In this position, current flows through the controlling terminals 26 of the time-delay relay 24. At the same time, the condenser 38 commences to charge. The charging of the condenser 38 continues until the controlled contacts 22 of the timedelay relay 24 under measurement close. At this point, the circuit through the windings it of the relay 20 is thereby closed and the contacts 44 are opened so that the condenser 38 immediately ceases charging. At the same time a second pair of contacts 59 of the relay 20 is closed, thus closing a circuit through a glow-tube 60, the lighting of which indicates to the operator that the reading may be taken. The reading is taken from the milliammeter 54, which is calibrated in terms of the correspondence between elapsed time and decrease in current. Such calibration is preferably linear.

Thus the operator may by reading the milliammeter 54 measure the time-delay between the application of voltage to the controlling terminals 26 of the time-delay relay 24 and the closing of the controlled contacts 22 thereof. It will be seen that the charge of the condenser 38 will remain since there is no discharge path with the contacts 44 open. It will, however, be understood that because of inherent leakage in the condenser 38 and grid currents in the tube 36, the reading must be taken within a fairly short time after the controlled contacts 22 close.

Calibration by adjustment may be made adjustment of the variable resistor 56 which shunts the meter 54 and the tap on the potentiometer 46. The time-delay of the time-delay relay 24 is a function of the. magnitude of the current through the controlling terminals 26. This current may be read on the milliammeter 32, and may be adjusted by the variable resistor 30. By successive adjustments of the variable resistor 30, the time-delay of the relay 24 may be measured for various values of such current.

Sample values for the circuit parameters of the embodiment of the invention shown in the drawing are as follows:

Voltage supply i volts 300 Potentiometer i2 ohms 5,000 Voltage-regulator tube I4 VR-l Voltage-regulator tube [6 VR-75 Milliammeter 32 ma 0-20 Vacuum tube 28 (SF-6 Variable resistor 30 ohms 5,000 Milliammeter 54 ma 0-6 Variable resistor 52 ohms 50 Vacuum tube m 6.15

4 Resistor 48 ohms 300 Potentiometer 65 do 25,000 Condenser 38 mfd 8 Resistor 40 ohms 25,000 Resistor 42 do 100,000

The exact embodiment illustrated in the drawing does not, of course, represent the only application of the teachings of this invention. Persons skilled in the art will readily devise equivalent circuits utilizing the teachings of this invention. Therefore, the invention shall be deemed to be limited only by the claims.

What is claimed is:

1. Apparatus for the measurement of elapsed? time comprising, in combination, an electronic tube having an anode, a cathode and a control. grid, a condenser connected between the control grid and the cathode, a bias voltage sourceadapted to charge the condenser so that the grid is biased negatively with respect to the cathode, charging means adapted to charge the condenser to a negative potential greater than the negative potential of the bias voltage source, switching means connected to said bias voltage source.- charging means and condenser simultaneously to disconnect the bias voltage source from, and connect the charging means to, the condenser at the commencement of a time under measurement, and indicating means responsive to changes in anode current of the electronic tube.

2. Apparatus for measuring the time-delay of tine-delay relay having controlling terminals and controlled contacts comprising, in combina tion: a first circuit including a source of potential, a pair of terminals adapted to be connected to the controlling terminals of the time-delay relay, and a first switch having an open and a closed position, all connected in series; a second circuit including a grid-controlled vacuum tube. a current meter in the plate circuit, a condenser connected between the grid and the cathode, a resistor in series with the grid, a grid-bias voltage supply having its positive terminal connected to the cathode and having terminals of respectively lesser and greater negative potential with respect to said cathode, and a second switch ganged with the first switch and connecting said resistor to the terminal of lesser negative potential when the first switch is in the open position and to the terminal of greater negative potential when the first switch is in the closed position; and relay means to open the connection between said resistor and said terminal of greater negative potential, said relay means being adapted to be actuated by the closing of the controlled contacts of the time-delay relay under measurement.

3. The apparatus of claim 2 wherein there is 1 provided a visual indicator and switching means coupled to the aforementioned relay means to actuate said visual indicator upon the closing of said controlled contacts.

CHARLES B. GOULD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,021,766 Bivens Nov. 19, 1932 2,269,603 Rockwcod Jan. 13, 1942 2,377,959 Richter June 12, 1945 

